Our specific aims are to improve the sensitivity and specificity of the antisera for thymine glycol (5,6-dihydroxy-5,6-dihydrothymine) and 8-hydroxyadenine (which are products of ionizing radiation) and to use these antisera in the radioimmunoassay to measure the production and repair of these lesions in normal cells vs. cells from patients with defective DNA repair (e.g., xeroderma pigmentosum, ataxia telangiectasia, Fanconi's anemia, etc.), dividing vs. non-dividing cells, old vs. young cells, terminally differentiated vs. less differentiated cells, intra- vs. internucleosomal DNA, and hetero- vs. euchromatin. Studies at the micro level will use fluorescent-labelled double antibody and autoradiography of 125I-labelled double antibody. Our long-term goal is to study the production and repair in cellular systems of DNA base damage caused by ionizing radiation or chemicals. This is a significant question in the field of radiation biology which has not been widely studied due to the lack of a generally applicable assay. The use of radioimmunoassay to study ionizing radiation-damaged bases is a new methodology in the field. Damaged bases are probable carcinogens. Thus, these studies should lead to a better understanding of the hazards of accidental radiation exposure and radiation used for diagnostic and therapeutic purposes.